This seems a little… conflicting. It's too formal for an angry tone. Replace it with something like:

I can have whatever the hell I want you little [DATA EXPUNGED].

Or you can leave your massive pile of insults in. Whichever you prefer, really.

SCP-[NUMBER UNDETERMINED]-J from being angered, though she still looks quite pissed I can assure you, she is much less active.

You usually want to refer to an SCP by their designation because it's professional, but you want to to that opposite here for the same reason. Maybe replace the whole thing with:

That cat from trying to claw my goddamn eyes out. She still looks like she's planning my fucking murder though. At least she naps most of the time.

And you might want to include a little bit at the end, something like this:

Right, right, procedures… "No personell are to enter SCP-XXXX's containment chamber unless SCP-XXXX has been drugged with at least one kilogram of… catnip…? Who the fuck ever wrote- oh. Okay, how drunk was I when I wrote this?

Seems like an interesting idea.

seems to have a general hate for the entire human population

I might replace that with:

seems to have a general hate for the entire human population An undying and vengeful desire to brutally murder every person on earth.(footnote)We have to differentiate her from other cats after all.

Test parameters: D-1 was dicking about in some room so we decided to put SCP-[NUMBER UNDETERMINED]-J in and see what would happen.

I feel like you don't capture the clinical tone of SCP articles. Maybe be less "funny" and more like a serious researcher who is trying to capture the description and properties of an anomalous object.

How so? If an author isn't familiar with clinical tone, telling them "you don't have clinical tone" doesn't give them much in the way of knowing how to fix that issue. If you're going to note tone as an issue, can you point out some examples of non-clinical tone and suggestions on how to improve it?

Maybe be less "funny" and more like a serious researcher who is trying to capture the description and properties of an anomalous object.

We have plenty of funny mainlisters written in excellent clinical tone. Some of our joke articles are written clinically. "Funny" in itself doesn't automatically mean "not clinical".

Again, can you provide an example of a portion of the draft that is too funny to be interpreted as clinical, and suggest how to improve that?

ETA: also, of note… this is a joke article. It's supposed to be funny.

Can you be more specific about why you found this funny? Or at least note which parts were funny, so the author has a better idea of your reaction beyond "it's funny"? Generic responses don't really help authors improve their work.

This collapsible is dedicated to looking at the material that brings down(or rather slows down) the overall punchline of your joke.

Grammar is up first.

SCP-[NUMBER UNDETERMINED]-J use this to not to avoid being seen but to annoy any people it come close to.

Some joke SCPs are purposefully written with bad grammar. This is not one of those SCP-Js and as such bad grammar will be noticed. In general, when bad grammar works against you it works against you hard. It makes a much larger impression than any joke you wish to make, and not the impression you want. In regards to corrections, I recommend going through the text after placing it through a dedicated word processor. That should correct most spelling and punctuation. After that, it's a little up to you to comb through your draft to catch what word processors don't, primarily sentences that are spelled correctly but don't make sense, such as the example I provided above. If it helps, I noticed dramatically more of them in the description so I would recommend starting there and working outwards.

Next up is point of view

though she still looks quite pissed I can assure you, she is much less active.

While grammar started off with an example of the types of problems you should be looking for throughout your piece, this issue is a little singular. This is the only time in the article, outside of the test logs, that first person is used. This is a little bit jarring since the rest of the article is written in mostly third person. I recommend being consistent, because a sudden change of style that fades as soon as it appears can snap immersion as soon as it appears because it can be perceived as an author mistake. This is the same argument as grammar.

Next up is tone.

D-1 was dicking about in some room so we decided to put SCP-[NUMBER UNDETERMINED]-J in and see what would happen.

The second janitor fainted presumably due to stress.

Now, tone is a little difficult to critique in joke article. This is because it can be difficult to determine whether or not tone is being sacrificed as part of the joke. That being said, we're going to revisit this in the next section. We're going to do this with the footnotes too.

So, as far as I've read, your joke rides on two or three pillars. Those pillars are the comedic tone, the footnote banter, and the fact that your SCP is just a household cat. I don't think these three work well together. The comedic tone comes off as a little immature and, combined with the grammatical issues, makes reading normal cat behavior through the eyes of the SCP kind of difficult. The footnotes end at the start of the article, so any comedic value they add dilutes, inevitably, when reading through the rest of your article. The rate of dilution is, again, not helped by the tone and grammatical issues.

I feel that the sentences are too long here. In other logs, it usually breaks actions up into individual sentences, like "Subject D-1 appears confused. Subject tried to pet SCP… etc, blah blah". You can see that every individual action is written with it's own sentence. You've kind stuffed them all into one sentence. it's good, but you could add that. TBH it's more of a nitpick, but still.

Also, (mega nitpick incoming) use words like "attempted" instead of tried, words like "obtained' instead of got, etc. This makes it sound more factual in areas you want (in a joke scp) to be factual.